This invention relates to a cell processing system for processing an ATM (asynchronous transfer mode) signal into an STM (synchronous transfer mode or synchronous transport module) signal and to a cell processing system for processing an STM signal into an ATM signal.
A conventional cell processing system of the type described comprises a first processing device, a second processing device, and an output selecting device connected to the first and the second processing devices. The first processing device receives an ATM signal or an STM signal as a first input signal and processes the first input signal into a first processed signal. The second processing device receives an ATM signal or an STM signal as a second input signal and processes the second input signal into a second processed signal. The output selecting device receives the first and the second processed signals and periodically and alternatingly selects one of the first and the second processed signals to output the one of the first and the second processed signals as an output signal. Namely, the output selecting device periodically switches the first and the second processed signals.
In this conventional cell processing system, the first and the second processing device must stop to process the first and the second input signals while the output selecting device switches the first and the second processed signals. Also, this conventional cell processing system must accept to cancel a part of the first or the second processed signal in the first or the second processing device when the first and the second processing device do not stop to process the first and the second input signals while the output selecting device switches the first and the second processed signals.